Vent structures for tank safety valves



Oct. 30, 1962 c. T. GRAVES 3,060,962

VENT STRUCTURES FOR TANK SAFETY VALVES Filed Jan. 23, 1961 2 Sheets-Sheet 1 FIG 1 l9 l3 IN V EN TOR.

Charles I Graves Oct. 30, 1962 c. T. GRAVES VENT STRUCTURES FOR TANK SAFETY VALVES 2 Sheets-Sheet 2 Filed Jan. 23, 1961 INVEN TOR. Charles I Graves United States Patent 3,660,962 VENT STRUCTURES FDR TANK SAFETY VALVES Charles '1. Graves, Gary, Ind, assignor to General American Transportation Corporation, Chicago, 111., a corporation of New York Filed Jan. 23, 1961, Ser. No. 84,270 Claims. (Cl. 137-587) The present invention relates to Vent structures for tank safety valves, and more particularly to such vent structures for safety valves incorporated in railway tank cars.

In a railway tank car that is employed in the transportation of flammable compressed gases, such as liquified petroleum gases (propane, butane, etc), liqui-fied hydrocarbon gases (rnethylamine, butadiene, methyl chloride, vinyl chloride, etc.), or the like, dome structure is provided in which there is incorporated control apparatus, including a safety valve of the pressure-relief type, so that the body of the tank car may be relieved of excessive pressure in order to prevent the possibility of rupture thereof under abnormal conditions.

While many tank safety valve venting arrangements have been employed heretoforefor the purpose noted, such arrangements have been subject to the general criticism that they are unduly complicated and substantially more expensive to manufacture than is desirable.

Accordingly, it is a general object of the present invention to provide an improved tank safety valve venting arrangement that is of improved and simplified construction and that is economical to manufacture and to maintain in proper Working order in service.

Another object of the invention is to provide a tank safety valve venting arrangement of the character noted that is incorporated in the bonnet cover of the bonnet structure that is provided upon the top of the manway cover plate of the manway structure communicating with the dome structure of a railway tank car; whereby both the safety valve incorporated in the manway cover plate and the interior of the bonnet structure are vented to the exterior.

A further object of the invention is to provide a safety valve and bonnet structure venting arrangement, wherein the bonnet cover for the bonnet structure incorporates an improved vent cover that accommodates both venting of the safety valve to the exterior and breathing between the interior of the bonnet structure and the exterior.

Further features of the invention pertain to the particular arrangement of the elements of the tank safety valve venting structure, whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification, taken in connection with the accompanying drawings, in which:

FIGURE 1 is a fragmentary side elevational view of the upper central portion of a railway tank car, illustrating the dome structure and the associated manway structure and the associated bonnet structure, and embodying the present invention;

FIG. 2 is an enlarged plan view of the bonnet cover for the bonnet structure, as shown in FIG. 1;

FIG. 3 is a greatly enlarged vertical sectional view of the vent structure and the associated vent cover carried by thebonnet cover, this view being taken in the direction of the arrows along the line 33 in FIG. 2;

FIG. 4 is an enlarged plan view, partly broken away, of the bonnet structure and the associated bonnet cover, as shown in FIG. 1, and illustrating the control apparatus housed in the bonnet structure; and

FIG. 5 is an enlarged combination side elevational view and vertical sec-tional view of the bonnet structure and 3,%,%Z Patented Oct. 30, 1962 the associated bonnet cover and the associated manway structure, 'as shown in FIG. 1, and also illustrating the control apparatus housed in the bonnet structure, this view being taken in the direction of the arrows along the offset line 5-5 in FIG. 4.

Referring now to FIG. 1 of the drawings, a fragmentary part of the upper central portion of a railway tank car 10 is there illustrated that comprises dome structure incorporating a safety valve venting arrangement embodying the features of the present invention. More partic ularly, the railway tank car 10 comprises a substantially cylindrical and horizontally disposed tank body 11, the upper central portion of which is shown and carries upstanding substantially cylindrical dome structure 12 terminating in upstanding substantially cylindrical manway structure 13. The top of the ma-nway structure 13 terminates in an outwardly directed surrounding flange 14 that carries a manway cover plate 15 that, in turn, carries upstanding substantially cylindrical bonnet structure 16, the lower portion of the bonnet structure 16 terminating in an outwardly directed surrounding flange 16a directly secured to the upper surface of the manway cover plate 15. In turn, the top of the bonnet structure 16 carries a bonnet cover 17; and the top of the bonnet cover 17 carries a vent cover =18. Also, the top of the dome structure 12 carries upstanding tubular structure 19 that is laterally offset with respect to the manway structure 13; which tubular structure 19 carries a siphon pipe, not shown, that projects downwardly through the dome structure 12, terminating adjacent to the bottom of the tank body 11; which siphon pipe carries valve structure, indicated at 2th and carried by the top of the tubular structure 19.

Referring now more particularly to FIGS. 4 and 5, it will be observed that the manway structure 13 defines an upstanding manway 21 therethrough communicating with the top of the dome structure 12, and that the annular flange 14 carried by the top of the manway structure 13 is suit-ably sealed to the bottom of the manway cover plate 15 by gland structure, indicated generally at 22, the manway cover plate 15 being securely held in place upon the annular flange 14 by an annular series of bolts 23. Also, it will be observed that the annular flange 16a carried by the bottom of the bonnet structure 16 is suitably secured to the top of the mianway cover plate 15 by an annular series of bolts 24. Further, the bonnet structure 16 defines a bonnet chamber therein, indicated generally at 25.

The manway cover plate 15 carries various control apparatus including a centrally disposed safety valve mechanism 39 of the poppet type for relieving excess pressure from the interior of the tank body 11 via the dome structure 12 and the manway structure .13. Specifically, the valve mechanism 311 includes an upstanding tubular valve seat 31 suitably secured and sealed in place in the upper portion of a centrally disposed opening 32 provided in the manway cover plate 15, as well as a poppet valve element 33 slidably mounted in the valve seat 31 and provided with an upper sealing element 34 selectively movable into open and closed positions with the extreme upper end of the valve seat 31. The poppet valve element 33 is provided with a depending stem 35 projecting downwardly into the manway 21 and carrying an associated surrounding coil spring 36 acting between the extreme lower end of the valve seat 31 and a fixture 37 carried by the extreme lower end of the stem 35. More particularly, the coil spring 36 biases the stem 35 downwardly so as to bias the valve elment 33 downwardly in order to bias the sealing element 34 into closed position with respect to the extreme upper end of the valve seat 31. Accordingl it will be understood that the valve mechanism 36 is normally biased into its closed position and is operative into its open position in response to an excess pressure within the manway 21, as a consequence of an excess pressure of the gas in the tank body 11 and in the dome structure 12. Of course, in the event of an excess pressure of the gas in the manway 21, the valve mechanism 30 is operated into its open position, the sealing element 34 unseating the extreme upper end of the valve seat 31 against the bias of the coil spring 36, whereby the gas in the manway 31 is throttled through the opening 32 in the manway cover plate 15 and thence through the valve seat 31 into the bonnet chamber 25.

In the arrangement, the upper end of the valve seat 31, as well as the sealing element 34, are surrounded by an upstanding exhaust pipe 38 that is secured at the extreme lower end thereof to a collar 39 that, in turn, is suitably secured and sealed to the outer surrounding flange portion 40 of the valve seat 31, the extreme upper end of the exhaust pipe 38 being open for a purpose more fully explained hereinafter. Accordingly, when the valve mechanism 38 is operated into its open position, the gas escaping from the manway 31 passes upwardly through the exhaust pipe 38, thereby relieving the excess pressure within the tank body 11. Of course, after the release of the excess pressure within the tank body .11, the valve mechanism 30 is automatically operated back into its normally closed position by virtue of the bias of the coil spring 36.

Also, the manway cover plate 15 carries three depending eduction pipes, two of which are illustrated at 41 and 42 in FIG. 5, which three eduction pipes extend downwardly through the manway structure 13 and the dome structure 12 into the lower portion of the tank body 11. More particularly, the three eduction pipes mentioned are suitably secured in place in three corresponding openings provided through the manway cover plate 15, and the extreme upper ends of the eduction pipes mentioned respectively carry three manually operable control valves 45, 46 and 47, as shown in FIG. 4, the three control valves 45, 46 and 47 being disposed in the bonnet chamber 25 in surrounding relation with respect to the exhaust pipe 38. The eduction control valves 45, 46 and 47 are identical, and as best shown in FIG. 5, the eduction control valve 45 is of the manually operable type, including a casing 50 provided with a side outlet normally closed byan associated plug 51. Also, the casing 50 houses valve mechanism, not shown, that is selectively operative between open and closed positions by corresponding manipulations of an associated manually operable handle 52. En the arrangement, the plugs 51, etc., carried by the casings 50, etc., of the three eduction control valves 45, 46 and 47 are directed radially outwardly toward three corresponding openings 53, etc., provided in the side wall of the bonnet structure 16; which three openings 53, etc., are respectively closed by three corresponding gates 54, etc., pivotally mounted upon the exterior surface of the bonnet structure 16, the gate 54 operatively associated with the opening 53 provided in the bonnet structure 16 being pivotally mounted upon the exterior surface of the bonnet structure 16 by a pivot pin 55, as illustrated in FIG. 5. Accordingly, it will be understood that after removal of the plugs 51, etc., the gates 54, etc., may be operated into their open positions, thereby to'accommodate the attachment of corresponding hoses to the casings 50, etc., of the eduction control valves '45, etc.; whereupon the eduction control valves 45, etc., may be selectively operated between their open and closed positions for the purpose of controlling the removal of the lading from the tank body 11 via the associated eduction pipes 41, etc., and into the respectively connected flexible hoses, not shown.

Also arranged within the bonnet chamber 25 is a suitable gauging device, indicated generally at 60 in FIG. 4; whereby the volume of the lading contained within the tank body 11 may be gauged in the usual manner. Of course, this gauging device 60 comprises structure extending through a corresponding opening provided through the manway cover plate 15. Further, the manway cover plate 15 carries a thermometer well fitting, indicated generally at 65 in FIG. 5, and depending therefrom through the manway 21 and thence through the dome structure 12 into the lower portion of the tank body 11; whereby the temperature of the lading may be tested, all in the usual manner. Of course, the thermometer well fitting 65 includes structure extending through an opening provided in the manway cover plate 15; which structure is closed by an associated cap, indicated at 66 in FIG. 4.

Referring now to FIGS. 1, 2, 4 and 5, the bonnet cover 17 is upwardly domed or contoured and is mounted for pivotal movements between open and closed positions with respect to the open top of the bonnet structure 16 by an arrangement including a pair of laterally spacedapart hinge elements 76 that receive a cooperating pintle ll that, in turn, is supported by a pair of spaced-apart hinge lugs 72. More particularly, the hinges 76 are suitably rigidly securcd to the exterior surface of the bonnet cover 17 adjacent to one side thereof and the two hinge lugs 72 are suitably rigidly secured to the corresponding adjacent exterior side of the bonnet structure 16 adjacent to the top thereof, the pintle 71 hinging together the hinge elements 70 and the hinge lugs 72, all in the usual manner. More particularly, the bonnet cover 17 is movable between a stable closed position, .as illustrated in FIGS. 1, 4 and 5, and a stable open position uncovering the top of the bonnet structure 16. In order to restrain the bonnet cover 17 in its stable open position and to prevent the same from falling outwardly onto the associated siphon control valve 20, a hinge stop 73 is suitably secured to the two hinges 70 and projecting thereabove; which hinge stop 73 engages to spaced-apart abutments 72a respectively carried by the hinge lugs 72. Also, the bonnet cover 17 carries a handle 74 rigidly secured to the hinges 70.

Further, the bonnet cover 17 carries a pair of spacedapart latch elements 75 located on the top surface thereof and positioned opposite to the pair of hinge elements 70; which latch elements 75 carry a pair of handles 76 and 77 rigidly secured thereto; whereby the bonnet cover 17 may be readily moved between its open and closed positions about the pintle 71 by the utilization of the handles 74, 76 and 77.

When the bonnet cover 17 occupies its closed position with respect to the bonnet structure 16, the pair of movable latch elements 75 cooperate with a pair of spacedapart stationary latch lugs 78 rigidly secured to the exterior surface of the bonnet structure 16 adjacent to the top thereof. Specifically, when the bonnet cover 17 occupies its closed position, the pair of latch elements 75 are disposed between the pair of latch lugs 73, as best shown in FIG. 4; and "aligned openings are provided through the outer ends of the latch elements 75 and the outer ends of the latch lugs 78 through which a removable latch rod 79 may be inserted for the purpose of restraining the bonnet cover 17' in its closed position with respect to the associated bonnet structure 16. As best illustrated in FIGS. 4 and 5, one end of the latch rod 79 includes an enlarged head 80, and the other end thereof includes a pivotally mounted keeper 31; whereby the keeper 81 restrains the latch rod 79 against displacement when the latch rod 79 occupies its inserted position through the aligned openings respectively provided through the latch elements 75 and the latch lugs 78. Moreover, the head 86 of the latch rod 79 may be suitably secured to one of the latch lugs 78 by an associated chain 82, as indicated in FIG. 5.

As best illustrated in FIGS. 3 and S, the central portion of the bonnet cover 17 has an opening formed therethrough in which there is arranged an upstanding tubular element 91 projecting both upwardly above the upper surface of the bonnet cover 17 and downwardly below the lower surface of the bonnet cover 17. More particularly, when the bonnet cover 17 occupies its closed position with respect to the bonnet structure 16, the tubular element 91 telescopes over the extreme upper end of the exhaust pipe 38, but in spaced relation radially with respect thereto, to provide an annular clearance gap, as indicated at 92 in FIG. 5, between the lower end of the tubular element 91 and the upper end of the exhaust pipe 38. Accordingly, in the arrangement, when the bonnet cover 17 occupies its closed position with respect to the bonnet structure 16, the tubular element 91 telescopes over the extreme upper end of the exhaust pipe 38 providing the annular clearance gap 92 between the interior of the tubular element 91 and the interior of the bonnet chamber 25. a

As best shown in FIGS. 2, 3 and 5, the vent cover 18 comprises a one-piece casing formed of non-sparking material, such, for example, as a suitable aluminum alloy or bronze, and preferably an aluminum alloy. More particularly, the vent cover 18 is of substantially inverted cup-shaped configuration including a top wall 95 provided with a downwardly directed shallow rim 96 having a plurality of cutouts 97 therein. Further, the vent cover 18 comprises a pair of spaced-apart hinge elements 98 carried by the upper surface thereof and pivotally connected by an associated pivot pin 99 to a stop lug 180 rigidly secured to the top surface of the bonnet cover 17 adjacent to the tubular element 91. Accordingly,'the vent cover 18 is movable between a stable closed position, as illustrated in solid lines in FIG. 3, and an unstable open position, as illustrated in dotted lines in FIG. 3. In order to insure the instability of the vent cover 18 in its open position, a stop 101 is formed thereon and positioned between the hinge elements 98; which stop 181 engages the extreme outer end of the stop lug 108 when the vent cover 18 is moved into its open position and while the vent cover 18 is in an inclined position with respect to the vertical. Accordingly, it will be understood that when the vent cover 18 occupies its closed position, the interior thereof communicates via the cutouts 97 provided in the rim 96 thereof with the exterior; and when the vent cover 18 is moved into its open position, the stop 101 engaging the stop lug 108 restrains the same in an unstable position so that it is subsequently returned by gravity from its unstable open position back into its stable closed position.

Referring now to FIGS. 3 and 5, it will be understood that in the event there is an exceedingly small excess pressure of the gas in the manway 21, the valve mechanism 30 may be opened only slightly or cracked, thereby to permit the escape of an exceedingly small amount of the gas from the tank body 11; whereby the small amount of gas escaping through the valve mechanism 30 in its cracked position proceeds upwardly through the exhaust pipe 38 and thence out of the upper end thereof into the tubular element 91 and consequently into the interior of the vent cover 18 in its closed position. This gentle escape of gas into the interior of the vent cover 18 in its closed position is vented via the cutouts 97 in the rim 96 of the vent cover 18 to the exterior, without operation of the vent cover 18 from its closed position. On the other hand, in the event of a substantial excess pressure in the manway 21, the valve mechanism 30 is operated into its substantially open position, with the result that the escaping gas rushes upwardly through the exhaust pipe 38 and thence through the tubular element 91 below the vent cover 18, thereby forcing the vent cover 18 from its closed position into its open position with the consequent escape of the gas to the exterior. Thereafter, when the gas escaping from the exhaust pipe 38 subsides, the vent cover 18 is returned by the action of gravity from its unstable open position back into its closed position.

Moreover, it will be appreciated that when both the bonnet cover 17 and the vent cover 18 occupy their closed positions, that breathing between the bonnet chamher 25 and the exterior, in either direction, may be effected through the cut outs 97 provided in the rim 96 of the vent cover 18 with the vent cover 18 in its closed position.

As previously explained, the vent cover 18 is formed of non-sparking material, while the bonnet cover 17 is normally formed of steel; and likewise, the bonnet structure 16, as well as the manway cover plate 15 are ordinarily formed of steel. Of course, the tank body 11, together with the dome structure 12, the manway structure 13, and the tubular structure 19 are ordinarily formed of steel. The arrangement, wherein the vent cover 18 is formed of non-sparking material is very advantageous, by virtue of the fact that the movement thereof between its open position and its closed position might otherwise offer the possibility of a spark into the escaping flammable gas; whereby this construction and arrangement of the vent cover 18 formed of non-sparking material substantially minimizes the fire hazard inherent in the venting of flammable gases from the body 11 of the railway tank car 10.

In view of the foregoing, it is apparent that there has been provided in a railway tank car, including dome structure, improved bonnet structure comprising an improved arrangement of the bonnet cover and the vent cover carried thereby with respect to the safety valve mechanism arranged Within the bonnet structure and accommodating the escape of excess gas pressure from the body of the tank car through the dome structure and thence through the bonnet structure and the bonnet cover to the exterior.

While there has been described what is at present considered to be the preferred embodiment of the invention, it Will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a tank including upstanding tubular manway structure defining a manway thereinto, a cover plate carried by the top of said manway structure and closing the top of said manway, said cover plate having a valve port therethrough, relief valve mechanism carried by said cover plate and cooperating with said valve port and operative in accordance with the gas pressure in said tank selectively to open and to close said valve port, upstanding tubular bonnet structure carried by said cover plate and provided with a top opening, a bonnet cover carried by the top of said bonnet structure and cooperating with said bonnet top opening and selectively movable between open and closed positions with respect thereto, said bonnet cover having a vent opening therethrough, a vent cover carried by the top of said bonnet cover and cooperating with said vent opening and selectively movable between open and closed positions with respect thereto, whereby operation of said relief valve mechanism into its open position effects the relief of excess gas pressure from said tank through said valve port and the consequent sudden increase in the gas pressure in said bonnet structure, and means normally biasing said vent cover into its closed position, whereby a sudden increase in the gas pressure in said bonnet structure effects movement of said vent cover from its normal closed position into its open position and the consequent relief of excess gas pressure in said bonnet structure through said vent opening followed by the return movement of said vent cover from its open position back into its closed position upon subsiding of the excess gas pressure in said bonnet structure.

2. In a tank including upstanding tubular manway structure defining a manway thereinto, a cover plate carried by the top of said manway structure and closing the top of said manway, said cover plate having a valve port therethrough, relief valve mechanism carried by said cover plate and cooperating with said valve port and operative in accordance with the gas pressure in said tank selectively to open and to close said valve port, upstanding tubular bonnet structure carried by said cover plate and provided with a top opening, a bonnet cover, first hinge mechanism cooperating between the top of said bonnet structure and one side of said bonnet cover for mounting said bonnet cover for selective movements between a stable open position and a stable closed position with respect to said bonnet top opening, said bonnet cover having a vent opening therethrough, a vent cover, and second hinge mechanism cooperating between the top of said bonnet cover and one side of said vent cover for mounting said vent cover for selective movements between an unstable open position and a stable closed position with respect to said vent opening, whereby said vent cover is normally biased into its closed position, whereby operation of said relief valve mechanism into its open position effects the relief of excess gas pressure from said tank through said valve port and the consequent sudden increase in the gas pressure in said bonnet structure, and whereby a sudden increase in the gas pressure in said bonnet structure effects movement of said vent cover from its stable closed position into its unstable open position and the consequent relief of excess gas pressure in said bonnet structure through said vent opening followed by the return movement of said vent cover from its unstable open position back into its stable closed position upon subsiding of the excess gas pressure in said bonnet structure.

3. In a tank including upstanding tubular manway structure defining a manway thereinto, a cover plate carried by the top of said manway structure and closing the top of said m'anway, said cover plate having a valve port theret-hrough, relief valve mechanism carried by said cover plate and cooperating with said valve port and operative in accordance with the gas pressure in said tank selectively to open and to close said valve port, an upstanding tubular relief valve stack carried by said cover plate, the bottom of said relief valve stack surrounding said relief valve port, upstanding tubular bonnet structure carried by said cover plate and surrounding said relief valve stack and provided with a top opening, a bonnet cover carried by the top of said bonnet structure and cooperating with said bonnet top opening and selectively movable between open and closed positions with respect thereto, said bonnet cover having a vent opening therethrough, an upstanding tubular vent stack carried by said bonnet cover and arranged in said vent opening, the bottom of said vent stack being disposed in alignment with and closely adjacent to the top of said relief valve stack when said bonnet cover is in its closed position, a vent cover carried by the top of said bonnet cover and cooperating with the top of said vent stack and selectively movable between open and closed positions with respect thereto, whereby operation of said relief valve mechanism into its open position effects the relief of excess gas pressure from said tank through said valve port and said relief valve stack into said vent stack when said bonnet cover is in its closed position and the consequent sudden increase in the gas pressure in said vent stack, and means normally biasing said vent cover into its closed position, whereby a sudden increase in the gas pressure in said vent stack effects movement of said vent cover from its normal closed position into its open position and the consequent relief of excess gas pressure in said vent stack through the top thereof followed by the return movement of said vent cover from its open position back into its closed position upon subsiding of the excess gas pressure in said vent stack.

4. The tank set forth in claim 1, wherein said vent cover is of substantially inverted cup-shaped configuration and the rim of said vent cover engages the adjacent top surface of said bonnet cover when said vent cover is in its closed position, and wherein the rim of said vent cover is discontinuous so as to provide a breathing hole therethrough accommodating gentle breathing of air into and out of said bonnet structure through said vent opening and through said breathing hole in series relation when both said bonnet cover and said vent cover are in their closed positions.

References Cited in the file of this patent UNITED STATES PATENTS 

